Biological and physiological action of growth hormone releasing hormone, growth hormone release inhibiting hormone, prolactin release inhibiting hormone, prolactin releasing hormone, thyrotropin releasing hormone, LH-releasing hormone, and FSH-releasing hormone will be evaluated using various in vivo, and vitro tests, and immunological methods. Effort will be concentrated in the first four hypothalamic hormones. These studies will be carried out in connection with purification and isolation work. When these hormones are isolated, characterized, and synthesized, the synthetic hormones and their analogues will be investigated for their physiological activity.